In general, semiconductor devices include wires (metal such as tungsten, aluminum, copper, titanium, titanium nitride wire, etc.) and contacts or vias connecting the wires.
Presently, wires are formed in multiple layers and design rules decrease, which enables highly integrated circuit. Now, a conventional formation method of metal wiring of a semiconductor device is described in detail with reference to the accompanying drawings. FIGS. 1a–1f are sectional views showing a formation method of metal wiring.
First, as shown in FIG. 1a, a lower titanium layer 2, an aluminum layer 3, an upper titanium layer 4, and a titanium nitride layer 5 are sequentially deposited on a semiconductor substrate 1 to form a metal multi-layered structure M of lower titanium/aluminum/upper titanium/titanium nitride. Alternatively, a lower titanium layer 2, a lower titanium nitride layer (not shown), an aluminum layer 3, an upper titanium layer 4, and an upper titanium nitride layer 5 are sequentially deposited to form a metal multi-layered structure M of lower titanium/lower titanium nitride/aluminum/upper titanium/upper titanium nitride. As a further alternative, a lower titanium layer 2, an aluminum layer 3, and an upper titanium layer 4 are sequentially deposited to form a metal multi-layered structure M of lower titanium/aluminum/upper titanium.
The metal multi-layered structure M applies to all multi-layered metal layers except the uppermost metal layer. If the metal multi-layered structure M applies to the undermost metal layer, state of a substrate is that contact holes filled up with tungsten plugs are formed in a pre metal dielectric (“PMD”). If the metal multi-layered structure M applies to the metal layer after the undermost metal layer except the uppermost metal layer, state of a substrate is that via holes filled up with tungsten plugs are formed in a inter metal dielectric (“IMD”) on a multi-layered metal layer that is patterned and sintered according to the design.
Next, as shown in FIG. 1b, the multi-layered structure is patterned and sintered to form metal wiring according to the design.
Subsequently, as shown in FIG. 1c, a lower layer 7 is formed using high density plasma (“HDP”) or spin on glass (“SOG”) methods to fill the gap. An interlayer insulating layer 8 is formed to an extent that surface configuration of the lower layer 7 is not shown and the interlayer insulating layer 8 is planarized using chemical mechanical polishing (“CMP”).
Subsequently, as shown in FIG. 1d, via holes 9 are formed in the interlayer insulating layer 8. During the etching process for forming via holes, the titanium nitride layer 5 and the upper titanium layer 4 are over-etched and the etching process is stopped at the aluminum layer 3 in the metal multi-layered structure M to reduce via hole resistance and decrease variation of via hole resistances in a wafer.
Then, as shown in FIG. 1e, a barrier metal layer having a multi-layered structure of titanium 10/titanium nitride 11 is formed in-situ on the interlayer insulating layer 8 including the via holes 9.
The titanium layer 10 of the barrier metal layer is formed to have a thickness between about 100–300 Å using sputtering method designed to be well-formed to narrow and deep via holes. The titanium nitride layer 11 is formed to have a thickness between approximately 80–150 Å using chemical vapor deposition (“CVD”) to improve the bottom step coverage of the barrier metal layer because the via holes become narrower and deeper due to high integration of semiconductor device.
Next, as shown in FIG. 1f, a tungsten layer 12 is formed to fill the via holes 9 fully or substantially fully. The tungsten layer 12 is planarized by CMP until the interlayer insulating layer 8 is exposed. Now, tungsten plugs 12 inside the via holes 9 are completed.
Alternatively, the tungsten layer 12 can be planarized by etching back the tungsten layer 12 until the barrier metal layer 11 on the interlayer insulating layer 8 is exposed.
Formation of via holes of a semiconductor device is completed using the above method, and the above process can be repeated as many as the number of the metal layers needed in a semiconductor device.
However, over shooting, which is generated when heat is applied during the CVD deposition of the titanium nitride layer, which is a part of a barrier metal layer, causes the aluminum layer to become loose.
Electrical connection of the semiconductor device is incomplete if the aluminum layer gets loose, which causes a defect in the semiconductor device.
Prior approaches to forming wiring using titanium include the following U.S. patents.
U.S. Pat. No. 6,436,823 discloses a wire formation technique using two-step annealing of titanium deposited on a silicon layer. U.S. Pat. No. 6,395,381 discloses a CVD having heat resistance, heat barrier, and heat shock. U.S. Pat. No. 5,136,362 discloses a formation method of a contact using titanium and titanium nitride. U.S. Pat. No. 6,313,027 discloses a method of preventing conductive material of aluminum from diffusing at a contact area during fabrication process, and so forth.